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Nutrient Role in Bioenergetics Chapter 4 Part 2 Bioenergetics-Glycolysis Carbohydrates primary function Energy for cellular work. Breakdown of 1 mole of glucose liberates 686 kCal of energy. • • 233 kCal (34%) usable The remainder dissipated as heat. Bioenergetics Glucose Degradation - glycolysis Occurs in two stages: • • 1. Anaerobic: Glucose breaks down relatively rapidly to 2 molecules of pyruvate → lactate 2. Aerobic: Pyruvate degrades further to carbon dioxide and water. Glycolysis Occurs in cytoplasm ATP required as phosphate donor Enzymes Glucose → glucose-6-phosphate ATP required as phosphate donor Fructose 6-phosphate Glycogenolysis Catabolism of muscle glycogen Glycogen phosphorylase Glucose-6-phosphate Epinephrine Glycolysis Glycolysis Hydrogen ions released during glycolysis NAD → NADH Additional 5 ATP molecules (ETC) Bioenergetics Aerobic glycolysis C3H4O3 – pyruvic acid Rest, light to moderate levels Hydrogen + Oxygen → H2O Bioenergetics Anaerobic NAD availability Lactate formation C3H4O3 + 2H+ → C3H6O3 Pyruvic Lactic Acid Acid Bioenergetics Aerobic C3H4O3 + 2H+ Pyruvic Acid C3H6O3 Lactic Acid The Cori Cycle: Lactate As a Fuel Source Fig 4.16 Bioenergetics Citric Acid Cycle (Krebs cycle). The second stage of carbohydrate breakdown Pyruvate converts to acetyl-CoA, degrades Carbon dioxide and hydrogen atomsmitochondria Most important function Generate H ions for Electron Transport Chain (ETC) Bioenergetics Bioenergetics Stored fat Largest source of potential energy. Supplies fatty acid molecules Energy sources for fat catabolism include: • Triacylglycerol Muscle fiber - stored Lipoprotein complexes - circulating Free fatty acids - circulating Bioenergetics Energy metabolism – lipolysis FFA + glycerol Form intracellular triglycerides Bind with intramuscular proteins Bioenergetics Adenosine 3’,5’-cyclic monophosphate Cyclic AMP - Hormonal effects Epinephrine, norepinephrine, glucagon, and growth hormone Bioenergetics Bioenergetics Glycerol • Provides carbon skeletons for glucose synthesis Fatty acids • • Beta (ß)-oxidation converts a free fatty acid to multiple acetyl-CoA molecules. Hydrogen ions oxidized through the respiratory chain. Bioenergetics Fats in CHO Flame FA breakdown requires CHO breakdown Intermediates of citric acid cycle Oxaloacetate (pyruvate) Malate Bioenergetics Lipogenesis The formation of fat Cytoplasm of liver cells Excess glucose or protein not metabolized Converted into stored triacylglycerol The lipogenic process requires: ATP energy B vitamins Biotin, niacin, and pantothenic acid. Bioenergetics Protein Energy substrate Endurance activities Heavy trainings. Deamination: Nitrogen removed from amino acid Pyruvate FA synthesis Bioenergetics Protein Catabolism facilitates water loss. The amine group of protein breakdown must be eliminated. “Obligatory” water as the waste products of protein catabolism leave the body dissolved in fluid (urine). Bioenergetics Bioenergetics Metabolic Mill The citric acid cycle Link Food energy and the chemical energy of ATP. Intermediates Mitochondrial membrane into the cytosol to synthesize bionutrients. Metabolic Mill